2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/11160Tunable filters are set to revolutionize many aspects of experimental astrophysics, particularly for applications in observational cosmology. After a summary of the fundamentals of classical spectroscopy, we present a review of the current technologies on offer. For extragalactic studies, small-gap etalons are the preferred option in terms of cost, photometric performance and throughput (e.g. the TAURUS Tunable Filter; http://www.aao.gov.au/).28 pages; Latex; 7 encapsulated postscript figures. In Atomic, Molecular and Optical Physics: Atoms and Molecules, vol. 29B, chapter 18, eds. F.B. Dunning and R.G. Hulet (Academic Press). Run latex twice for table of contentsAstrophysicstext